Reinforced ply material with untwisted sets of steel monofilaments

ABSTRACT

Reinforced ply material having a plurality of reinforcement elements (e.g., steel monofilaments) embedded in an elastomeric (e.g., rubber) sheet. The reinforcement elements are grouped in untwisted sets and each set includes a plurality of reinforcement elements. In an apparatus and/or method for making the reinforced ply material, the reinforcement elements are guided by a guide insert having passages corresponding to the desired grouped arrangement of the reinforcement elements. The reinforced ply material can be used to make steel belts for pneumatic tires.

FIELD OF THE INVENTION

[0001] This invention relates generally to a reinforced ply material andmore particularly to a reinforced ply material which can be used in theproduction of steel belts for pneumatic tires.

BACKGROUND OF THE INVENTION

[0002] Reinforced ply material commonly comprises an elastomeric (e.g.rubber) sheet and a plurality of reinforcement elements embeddedtherein. When the ply material is being used to make steel belts forradial tires, the reinforcement elements are usually cabled steel cordswhich are arranged in a planar row with uniform lateral spacing betweenthe cords. Such ply materials are typically manufactured with anapparatus including a guide insert having passages through which thecabled steel cords pass. Specifically, the guide insert is positionedjust upstream of a die throat so that the pattern of its passagesdictates the arrangement of the cabled steel cords in the reinforced plymaterial and thus the steel belt.

SUMMARY OF THE INVENTION

[0003] The present invention provides reinforced ply material whereinsteel monofilaments can be used as the reinforcement elements instead ofcabled steel cords. Monofilaments are insert definition of“monofilament”. When compared to cabled steel cord, steel monofilamentsare more economically made and require less rubber to coat in anextrusion process. Accordingly, the reinforced ply material of thepresent invention can provide an economic alternative for makingreinforced ply material for the production of steel belts for pneumatictires.

[0004] More particularly, the present invention provides reinforced plymaterial comprising an elastomeric sheet (e.g., rubber) and a pluralityof reinforcement elements embedded therein. The reinforcement elementsare grouped in untwisted sets and each set includes a plurality ofreinforcement elements. Adjacent reinforcement elements in the same setare spaced apart an intra-set distance and adjacent reinforcementelements in different sets are spaced apart a greater inter-setdistance. This arrangement of the reinforcement elements makes itpossible to use untwisted groups of mono-filaments in place of cabledsteel cords.

[0005] In an apparatus and/or method for making the reinforced plymaterial of the present invention, the reinforcement elements are guidedaccording to the desired arrangement and the guided reinforcementelements are encapsulated in an elastomeric extrudate. The guidingfunction can be performed by a guide insert having passages arrangedcorresponding to the desired arrangement of the reinforcement elementsin the ply material. For example, the guide insert can comprise apassage for each set of reinforcement elements and such passages canhave circular or rectangular cross-sectional shapes. Alternatively, theguide insert can comprise a passage for each reinforcement element withthe passages grouped in sets corresponding to the sets of reinforcementelements.

[0006] The present invention provides these and other featureshereinafter fully described and particularly pointed out in the claims.The following description and drawings set forth in detail certainillustrative embodiments of the invention. These embodiments areindicative, however, of but a few of the various ways in which theprinciples of the invention can be employed.

DRAWINGS

[0007]FIG. 1 is a perspective view, partly in section of reinforced plymaterial according to the present invention.

[0008]FIG. 2 is a cross-sectional view of a tire incorporating a steelbelt made from reinforced ply material according to the presentinvention.

[0009]FIG. 3 is a plan view, partly broken away and in section, of anapparatus for making the reinforced ply material of the presentinvention.

[0010]FIG. 4 is an enlarged sectional view taken on line 4-4 in FIG. 3.

[0011]FIG. 5 is a sectional view taken on line 5-5 in FIG. 4.

[0012]FIG. 6 is an exploded perspective view of a crosshead die of theapparatus.

[0013]FIG. 7 is an isolated view of a guide insert of the crosshead die.

[0014]FIG. 8 is an enlarged schematic view of front end of the guideinsert showing one possible arrangement of passages and reinforcementelements passing therethrough.

[0015]FIG. 9 is a view similar to FIG. 8, showing another possiblearrangement of passages and reinforcement elements passing therethrough.

[0016]FIG. 10 is a view similar to FIGS. 8 and 9, showing a furtherpossible arrangement of passages and reinforcement elements passingtherethrough.

DETAILED DESCRIPTION

[0017] Referring now to the drawings and initially to FIG. 1, reinforcedply material 20 according to the present invention is shown. The plymaterial 20 comprises an elastomeric sheet 22 and a plurality ofreinforcement elements 24 embedded therein. The sheet 22 can be made ofrubber or any other suitable elastomer. The reinforcement elements 24can be of any suitable material, however, the arrangement of thereinforcement elements 24 makes it possible to use steel monofilamentswhen the ply material is to be used to make steel belts for pneumatictires.

[0018] In the ply material 20, the reinforcement elements 24 arepositioned in one planar row, however, the spacing between each of thereinforcement elements 24 is not uniform. Instead, a plurality ofparallel and untwisted reinforcement elements 24 are grouped inuntwisted bundles or sets 26 a, 26 b, 26 c, etc. Within each set 26, theintra-set distance between reinforcement elements 24 is preferablysubstantially the same. Also, the inter-set distance between adjacentbut not-the-same-set reinforcements elements 24 (in other words thedistance between adjacent sets 26) is preferably substantially the same.The inter-set distance is greater than the intra-set distance.

[0019] The number of sets 26, the number of reinforcement elements 24 ineach set, the diameter FD of the elements 24, the intra-set distance,and/or the inter-set distance are selected to satisfy the requirementsof the intended use of the reinforced ply material 20. For example, theply material 20 can contain between about 100 and about 220 sets,between about 120 and about 200 sets, between about 140 and about 180sets, and/or between about 150 and about 170 sets. Each set 26 cancontains between 2 and 8 reinforcement elements 24, between 3 and 6reinforcement elements 24, between 3 and 4 reinforcement elements,and/or 3 reinforcement elements 24. Each of the elements 24 has adiameter FD of about 0.20 mm to about 0.30 mm, about 0.22 mm to about0.28 mm, about 0.24 mm to about 0.26 mm, about 0.25 mm, and/or about0.26 mm. The intra-set distance is between about 0.00 mm (i.e., theelements are touching) and about 0.30 mm, between about 0.00 mm andabout 0.26 mm, between about 0.00 mm and 0.20 mm, and/or between about0.00 mm and about 0.10 mm. The inter-set distance is between about 0.25mm and about 0.50 mm, between about 0.30 mm and about 0.45 mm, and/orbetween about 0.35 mm and about 0.40 mm.

[0020] In the illustrated and preferred embodiment, the ply material 20has between 150 and 170 sets 26 and there are three reinforcementelements 24 in each set 26. The diameter FD of each of the reinforcementelements 24 is either about 0.25 mm or about 0.26 mm, the intra-setdistance is between about 0.00 mm (i.e., touching) and about 0.20 mm,and the inter-set distance is between about 0.35 mm and about 0.40 mm.These groupings and dimensions are believed to be compatible with anextrusion manufacturing process and also acceptable for use of the plymaterial 20 as a steel belt in a pneumatic tire. Specifically, forexample, the ply material 20 can be severed into strips, the stripsoriented at preselected biases and stitched end-to-end to produce asteel belt 28 for a pneumatic tire 30 as shown in FIG. 2.

[0021] Other shapes of the sheet 22 and/or other arrangements of thereinforcement elements 24 are possible with and contemplated by thepresent invention. For example, although the illustrated ply materialhas a generally rectangular ribbon shape, other forms of the sheet(e.g., curved, tubular) can be used in certain circumstances.Additionally or alternatively, the sets can contain different numbers ofreinforcement elements, reinforcement elements can be non-uniformlyspaced within sets, and/or sets can be spaced apart varying distancesfrom each other.

[0022] Referring now to FIGS. 3-6, an apparatus 40 for making thereinforcement ply material 20 according to the present invention isshown. The apparatus 40 includes an extruder 42 and a cross-head die 44into which an elastomeric material is extruded. The reinforcementelements 24 enter the die 44 and are encapsulated with the extrudethereby forming a ribbon of reinforced ply material 20 which emergesfrom the opposite side of the die 44.

[0023] The die 44 comprises upper and lower die blocks 50 a and 50 b,mating die plates 52 a and 52 b, discharge bars 54 a and 54 b, and aguide insert 56. The die blocks 50 embrace the die plate 52 and thedischarge bars 54 and the die plates 52 embrace the guide insert 56.Inner surfaces of the die blocks 50 and outer surfaces of the die plates52 are complementally shaped to form an annual extrude channel 60 and athroat 62 around the die plates 52. Inner relatively flat surfaces ofthe die plates 52 form an emitting slot 64 from the rear of the die 44to the guide insert 56. Inner relatively flat surfaces of the dischargebars 54 form a discharge slot 66 positioned just upstream the throat 52and the guide insert 56.

[0024] During operation of the apparatus 40, the extruder 42 deliversthe elastomeric material (e.g., rubber) and it flows under pressurethrough the channel 60, through the throat 62 and through the dischargeslot 66. Simultaneously, the reinforcement elements 24 are moved thoughthe passage 64, through the guide insert 56 and into the discharge slot66. As the elements 24 emerge from the guide insert 56, they areencapsulated by the extrudate.

[0025] Referring now to FIG. 7, the guide insert 56 is shown isolatedfrom the rest of the apparatus 40. The guide insert 56 has a body 70having a rear portion 72 and a front portion 74, which together defineguide passages 76. The insert's rear portion 72 is shaped and sized forinserted engagement with the die plates 52 and the insert's frontportion 74 is shaped and sized to suitably define the die throat 62 and,to this end, has an arrow-like shape. The passages 76 extend from theend wall of the rear portion 72 to the apex of the front portion 74 (SeeFIG. 4.)

[0026] The passages 76 transversely and laterally guide thereinforcement elements 24 into the die throat 62 and thus define theposition and spacing of the elements 24 in the reinforced ply material20. Thus, the passages 76 are all transversely aligned on the same planeto form a single row of reinforcement elements 24. Also, the lateralspacing of the passages 76 corresponds to the desired lateral spacingthe elements 24, that is, in the preferred and illustrated embodiment,uniformly spaced sets 26 of the elements 24.

[0027] Referring now to FIG. 8, one possible configuration for the guidepassages 76 is shown. In this insert configuration, the passages 76 arecircular in cross-section and three reinforcement elements 24 passthrough each passage 76 to form one set 26 of elements. Each of thepassages 76 has a hole diameter HD which accommodates the parallelpositioning of three elements 24 with an appropriate cushion (e.g.,about 10%, 15% or 20% FD.) Intra-set elements 24 can touch (i.e., theintra-set distance is about 0.00 mm) in this arrangement and insertmanufacture is similar to that of conventional guide inserts for cabledsteel cords. The open spaces above and below the reinforcement elements(in the illustrated orientation) may increase the potential for twistingand/or transverse misalignment between intra-set reinforcement elements24. Tension-maintaining devices and/or rollers can be employed to keepthe elements 24 co-planar as they enter and pass through the guideinsert 56.

[0028] Referring now to FIG. 9, another insert configuration is shown inwhich the passages 76 have rectangular cross-sections. As with theconfiguration shown in FIG. 8, three reinforcement elements 24 passthrough each passage 76 to form one set 26 of elements. Each of thepassages 76 has a hole diameter HD (e.g., the length of the rectangle)which accommodates the parallel positioning of three elements 24 with anappropriate cushion. When compared to the circular passages, therectangular shape eliminates the space above and below the elements 24thereby minimizing the potential for transverse misalignment. However,this insert design may be more difficult and/or more expensive tomanufacture.

[0029] In the insert configurations shown in FIGS. 8 and 9, the passages76 are spaced apart, or have an external land area EL, corresponding tothe inter-set distance of the reinforcement elements 24. The number ofsets 26 of reinforcement elements is dictated by the maximum span (i.e.,greatest allowable lateral distance between the first and last passage)of the insert and the diameter FD of the reinforcement elements 24. Forexample, for an insert having 203.2 mm span (8 inches) and reinforcementelements 24 having an 0.25 diameter, 168 sets would be used. For thesame insert span with reinforcement elements 24 having an 0.26 diameter,157 sets would be used. Some sample specification calculations are asfollows: HD Σ HD Σ Non-HD EL Cushion (mm) (mm) (mm) (mm) EL/FD Span =203.2 mm FD = 0.25 mm 168 Sets 10% 0.825 138.81 64.39 0.39 1.54 15%0.863 145.12 58.08 0.35 1.39 20% 0.900 151.42 51.78 0.31 1.24 Span =203.2 mm FD = 0.26 mm 157 Sets 10% 0.858 134.94 68.26 0.44 1.68 15%0.897 141.08 62.12 0.40 1.53 20% 0.936 147.21 55.99 0.36 1.38

[0030] In addition to providing the inter-set land distance EL betweenadjacent sets 26, the table displays the resulting ratio EL/FD whichrepresents the size of the space between sets (EL) relative to thediameter of the reinforcement element (FD). If the reinforcement ply 20is to be used for steel belts, a larger ratio is believed to bedesirable. Thus, using a 10% cushion produces the best twospecifications, with the 0.26 mm diameter producing the better of thesetwo. Along this line, it is noted that when cabled steel cord is beingused, the cushion is usually about 0.152 mm larger than the cord toaccommodate welds. However, if steel monofilament without welds are usedfor the reinforcement elements 24, this cushion can be reducedconsiderably. Thus, with steel monofilaments, the smaller cushion (e.g.,10%) can be used thereby increasing the EL/FD ratio.

[0031] Referring now to FIG. 10, a further passage configuration for theinsert 56 is shown. In this insert configuration, a passage 76 isprovided for each reinforcement element 24 and the passages are groupedin sets of three. This design has the advantage of assuring theco-planar positioning of the elements 24 in a single row. This designhas the disadvantages of not allowing the intra- set reinforcementelements 24 to touch (ie., the intra-set distance is greater than about0.00 mm). Also, this design can also be more complicated and/or moreexpensive than designs in which intra-set reinforcement elements sharethe same passage.

[0032] The inter-set land area EL in this embodiment corresponds to thedistance between adjacent sets of passages and the internal land area ILcorresponds to the distance between intra-set passages. In designing theinsert 56, the inter-set land area EL is compared to the span of eachpassage set or, in other words, the sum of diameters of the holes andsum of the internal land area (IL) between the holes. A significantdesign factor is that there is a minimum distance (e.g., between 0.110mm and 0.254 mm) which can be achieved between holes and this distancerepresents the lower limit of the IL dimension. This design limitationcan be the controlling factor in the selection of set-to-set spacing. Asshown in the sample specifications below, some designs are not possiblebecause the EL dimension would have to be negative or less than thisminimum distance. Σ HD + HD IL Σ IL Σ Non-HD EL Cushion (mm) (mm) (mm)(mm) (mm) EL/IL EL/FD Span = 203.2 mm FD = 0.25 mm 168 Sets 10% 0.2750.254 224.28 −21.08 — — — 0.127 181.54 21.66 0.13 1.02 0.52 0.110 175.8227.38 0.16 1.49 0.65 15% 0.288 0.254 230.59 −27.39 — — — 0.127 187.8515.35 0.09 0.72 0.37 0.110 182.13 21.07 0.13 1.15 0.50 20% 0.300 0.254236.90 −33.70 — — — 0.127 194.16 9.04 0.05 0.43 0.22 0.110 188.44 14.760.09 0.80 0.35 Span = 203.2 mm FD = 0.26 mm 157 Sets 10% 0.254 214.84−11.64 — — — 0.127 174.89 28.31 0.18 1.43 0.70 0.110 169.54 33.66 0.221.96 0.83 15% 0.254 220.97 −17.77 — — — 0.127 181.03 22.17 0.14 1.120.55 0.110 175.68 27.52 0.18 1.60 0.68 20% 0.254 227.11 −23.91 −0.15 — —0.127 187.16 16.04 0.10 0.81 0.39 0.110 181.81 21.39 0.14 1.24 0.53

[0033] In these calculations, the EL/IL represents the relation betweenthe inter- set distance (EL) and the intra-set distance (IL).(Accordingly, if this ratio equals one, the reinforcement elements 24are all equally spaced.) It is believed that when the reinforced plymaterial 20 is used for the production of steel belts 28, this ratioshould be as high as possible thereby making the 10% cushion with thesmallest possible internal land IL dimension the best candidates. Again,if the reinforcement elements 24 are “weld-less” steel monofilaments (asopposed to cabled steel cord), a 10% cushion can be possible.

[0034] One can now appreciate that present invention provides areinforced ply material 20 and a method of making the same which allowsthe use of steel monofilaments for the reinforcement elements 24.Although the invention has been shown and described with respect tocertain embodiments, it is obvious that equivalent alterations andmodifications will occur to others skilled in the art upon the readingand understanding of this specification. The present invention includesall such alterations and modifications and moreover is limited only bythe scope of the following claims.

1. Reinforced ply material comprising an elastomeric sheet and aplurality of reinforcement elements embedded therein; wherein thereinforcement elements are grouped in untwisted sets and each setcontains a plurality of reinforcement elements; wherein adjacentreinforcement elements in the same set are spaced apart an intra-setdistance and adjacent reinforcement elements in different sets arespaced apart an inter-set distance; and wherein the inter-set distanceis greater than the intra-set distance.
 2. Reinforced ply material asset forth in claim 1, wherein the intra-set distance is substantiallythe same between the reinforcement elements.
 3. Reinforced ply materialas set forth in claim 1, wherein the inter-set distance is substantiallythe same between the sets of reinforcement elements.
 4. Reinforced plymaterial as set forth in claim 1, wherein the reinforcement elements arepositioned in a single planar row.
 5. Reinforced ply material as setforth in claim 1, wherein each set contains the same number ofreinforcement elements.
 6. Reinforced ply material as set forth in claim1, wherein the reinforcement elements are steel monofilaments. 7.Reinforced ply material as set forth in claim 6, wherein the intra-setdistance is substantially the same between the reinforcement elements,wherein the inter-set distance is substantially the same between thesets of reinforcement elements, wherein the reinforcement elements arepositioned in a single planar row, and wherein each set contains thesame number of reinforcement elements.
 8. Reinforced ply material as setforth in claim 6, comprising between about 100 and about 220 sets ofreinforcement elements, wherein each set comprises between 2 and 8reinforcement elements, and wherein each reinforcement element has adiameter of about 0.20 mm to about 0.30 mm.
 9. Reinforced ply materialas set forth in claim 8, comprising between about 150 and about 170 setsof reinforcement elements, wherein each set comprises 3 reinforcementelements, and wherein each reinforcement element has a diameter of about0.25 mm to about 0.26 mm.
 10. Reinforced ply material as set forth inclaim 6, wherein the intra-set distance is between about 0.00 mm andabout 0.30 mm and wherein the inter-set distance is between about 0.25mm and about 0.50 mm.
 11. Reinforced ply material as set forth in claim10, wherein the intra-set distance is between about 0.00 mm and about0.20 mm and wherein the inter-set distance is between about 0.10 mm and0.50 mm.
 12. Reinforced ply material as set forth in claim 11, whereinthe intra-set distance is about 0.00 mm.
 13. Reinforced ply material asset forth in claim 11, wherein the inter-set distance is between about0.30 mm and 0.50 mm.
 14. Reinforced ply material as set forth in claim1, wherein the elastomeric sheet is made of rubber.
 15. A steel beltmade from the reinforced ply material of claim
 1. 16. A pneumatic tireincorporating the steel belt of claim
 15. 17. An apparatus for makingthe reinforcement ply material of claim 1, comprising an extruder and adie head into which the extruder extrudes an elastomeric material;wherein the die head defines a die throat and includes a guide insertwhich guides the reinforcement elements into the die throat; and whereinthe guide insert comprises passages through which the reinforcementelements pass and which are arranged in a pattern corresponding to thearrangement of the reinforcement elements in the reinforced plymaterial.
 18. An apparatus as set forth in claim 17, wherein the guideinsert includes a passage for each set of reinforcement elements andwherein the passages are laterally spaced from each other a distancecorresponding to the inter-set distance.
 19. An apparatus as set forthin claim 18, wherein the lateral distance between passages is betweenabout 0.20 mm and about 0.50 mm.
 20. An apparatus as set forth in claim19, wherein the lateral distance between passages is between about 0.30mm and 0.45 mm.
 21. An apparatus as set forth in claim 20, wherein thepassages are circular in cross-section shape.
 22. An apparatus as setforth in claim 20, wherein the passages are rectangular in cross-sectionshape.
 23. An apparatus as set forth in claim 17, wherein the guideinsert includes a passage for reinforcement elements and the passagesare grouped in sets corresponding to the sets of reinforcement elements,wherein intra-set passages are spaced apart a lateral distancecorresponding to the intra-set distance, and wherein inter-set passagesare spaced apart a greater lateral distance corresponding to theinter-set distance.
 24. An apparatus as set forth in claim 23, whereinthe distance between intra-set passages is between about 0.11 mm andabout 0.13 mm, and wherein the distance between inter-set passages isbetween about 0.13 and about 0.23 mm.
 25. A guide insert for insertioninto a die head to make the reinforced ply material of claim 1, saidguide insert comprising a body and passages which extend through thebody and which are arranged in a pattern corresponding to thearrangement of the reinforcement elements in the reinforced plymaterial.
 26. A guide insert as set forth in claim 25, wherein the bodyincludes a passage for each set of reinforcement elements and thepassages are laterally spaced from each other a distance correspondingto the inter-set distance.
 27. A guide insert as set forth in claim 26,wherein the lateral distance between passages is between about 0.20 mmand about 0.50 mm.
 28. A guide insert as set forth in claim 27, whereinthe lateral distance between passages is between about 0.30 mm and 0.45mm.
 29. An guide insert as set forth in claim 26, wherein the passagesare circular in cross-section shape.
 30. A guide insert as set forth inclaim 26, wherein the passages are rectangular in cross-section shape.31. A guide insert as set forth in claim 25, wherein the body includes apassage for reinforcement elements and the passages are grouped in setscorresponding to the sets of reinforcement elements, wherein intra-setpassages are spaced apart a lateral distance corresponding to theintra-set distance, and wherein inter-set passages are spaced apart agreater lateral distance corresponding to the inter-set distance.
 32. Aguide insert as set forth in claim 31, wherein the distance betweenintra-set passages is between about 0.11 mm and about 0.13 mm, andwherein the distance between inter-set passages is between about 0.13and about 0.23 mm.
 33. A method for making the reinforced ply materialof claim 1, said method comprising the steps of: guiding thereinforcement elements in a path corresponding to their arrangement inthe reinforced ply material; and encapsulating the guided reinforcementelements in an elastomeric extrude.
 34. A method as set forth in claim33, wherein said guiding step comprises inserting a guide insert into adie head so that the guide insert guides the reinforcement elements intoa die throat, wherein the guide insert comprises passages through whichthe reinforcement elements pass, and wherein the passages are arrangedcorresponding to the arrangement of the reinforcement elements in thereinforced ply material.